Objectives The ecological stoichiometric characteristics of C, N, P and K of Pinus massoniana were investigated, which would provide references for the nutrient management during the growth of P. massoniana plantation.
Methods Standing age of 10 years, 20 years, 30 years, 36 years of P. massoniana plantation were selected as research objects in Mengguan Forest Farm in central Guizhou. In 20 m × 20 m typical plots of each standing age, plant samples were collected and divided into leaves, stems and roots for the determination of C, N, P, K contents. The stoichiometric ratio were calculated and compared in a spatial scale.
Results 1) The element content and stoichiometric ratios in each organ fluctuated with the increase of stand age. The C and N contents in leaves showed an upward trend with stand ages, while the P and K contents increased first and then decreased. The C content in stems showed an upward trend while the N and K contents decreased first and then increased, and the P content was relatively stable with stand ages (P > 0.05). The C content in root was not significantly changed with the stand age (P > 0.05), the N contents showed a trend of first decreasing and then increasing, and the content of P increased first and then decreased, the K content showed a ‘decline–rise–decline’ trend. Leaf C∶N showed a decreasing trend with the increase of stand age, while N∶P decreased first and then increased, P∶K increased first and then decreased and then slightly increased. Stem C∶N showed no significant change with the increase of stand age (P > 0.05), N∶P decreased first and then increased, P∶K increased first and then decreased. Root C∶N and P∶K increased first amd then decreased, N∶P decreased first and then increased. The changes of C∶P, C∶K and N∶K of each organ were not significant with the stand age (P > 0.05). 2) C content in different organs was 436.6–468.2 g/kg, shown as stem > leaf > root. N content was 1.45–2.90 g/kg, shown as stem > root > leaf. The contents of P and K were 0.14–1.05 g/kg and 0.53–5.06 g/kg respectively, which were both in order of leaf > root > stem. C∶N was 165.4–311.4, leaf > root > stem; C∶P, C∶K, N∶P, N∶K were 440.1–3745, 92.14–1311, 1.48–23.4, 0.31–7.97, respectively, which were all in order of stem > root > leaf. P∶K was 0.20–0.36, shown as stem > leaf > root. 3) The leaf, stem and root C∶N and N content, C∶P and P content, C∶K and K content were all significantly and negatively correlated (P < 0.01), and the C∶N, C∶P, C∶K and C content were not significantly correlated (P > 0.05).
Conclusions Compared with the subtropical region in the same latitude, the contents of C, N and K in P. massoniana are relatively low in this region, and that of P is relatively high. The nutrient contents and stoichiometric ratios vary in organs of P. massoniana at different ages. The leaf N∶P ratios is in range of 1.11–1.85 in all the stand ages, so the growth of forest is generally restricted by N. In the young and middle stand age of plantations, N fertilizer application is suggested to maintain the normal growth, and small rate of K fertilizer is recommended , and phosphate is not necessary.
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